Dictyota, as a diverse genus of the family Dictyotaceae (brown algae) in warm temperate to tropical seas, is characterized by high morphological plasticity. The wide range of morphological variation in the members of this genus makes the species distinction based on morphological or anatomical features complicated. Persian Gulf and Gulf of Oman as a subregion of subtropical marine environments in south of Iran has various species of Dictyotaceae. This study investigated the taxonomy of Dictyota as one main tropical genus of the family Dictyotaceae in southern coastlines of Iran. In the current study DNA sequences of the two genes rbcL and Cox3, as well as their morphological features were analyzed to determine the species distinction of the genus in the studied areas. In rbcL phylogenetic tree, some of the sequences obtained from Iranian specimens of Dictyota formed a fully supported new clade with four sequences obtained from specimens collected from Mayotte, Bermuda, Netherland Antilles and Bahamas (Caribbean Sea). In Cox3 phylogenetic analyses, the sequences of the specimens from Iran were grouped with two sequences of Dictyota specimens collected from Egypt and Bahamas. The results showed the new clade in both rbcL and Cox3 tree represent a distinct new taxon with anastomosing points between overlaps blades which led to cushion-like (pulvinus) habit as diagnostic characteristic, so, the taxon is introduced as the new species Dictyota pulvinata sp. nov. The sequences of another species of Dictyotaceae in the current study were grouped with the sequences of Canistrocarpus cervicornis from Florida in United States of America, where the type specimen of Canistrocarpus cervicornis has already been reported.